Some banks are willing to pay £200 to acquire a new customer e.g. Nationwide £100 to the existing customer and £100 to the new customer. Nationwide will spend multiple millions on this every month.
Monzo won’t beat £200 switch incentive so perhaps we could get a little bit more creative. I wonder if Monzo could set up a weekly prize draw where, if you’ve had your salary paid in that month or successfully referred a new customer (or whatever other behaviours Monzo wish to promote - perhaps more than one entry ticket the more boxes you tick), then you can login to the app on a Friday (more app interactions - a metric used to measure growth), hit a button and opt in to the draw. The draw could be for 1,000 x £100, for example, or tiered with a big winner of £10k and reducing prizes down to £10 to a larger number of people. Or it could be that the draw occurs once per month on the week before payday and framed as “Monzonaught Rocket Boost” to help you through to payday.
This would generate some hype and sign-ups. I suspect there could be gambling laws around this and that’s maybe why it’s not been done by other banks to-date. It’s not too dissimilar to the NS&I Premium Bonds though